Aqueous slurries of triethanolamine salts of linear alkylbenzene sulfonic acids



United States Patent 3,463,736 AQUEOUS SLURRIES 0F TRIETHANOLAMINE SALTS 0F LINEAR ALKYLBENZENE SUL- FONIC ACIDS John C. Reid, Wynnewood, Robert B. Doan, Drexel Hill, and Robert C. Taylor, King of Prussia, Pa., assignors to Atlantic Richfield Company, New York, N.Y., a corporation of Pennsylvania No Drawing. Filed Mar. 4, 1966, Ser. No. 531,737 Int. Cl. C11d 1/40, 1/14 US. Cl. 252152 8 Claims ABSTRACT OF THE DISCLOSURE This invention relates to aqueous detergent slurries comprising the triethanolamine salt of an alkylbenzene sulfonic acid having a linear alkyl radical ranging from 8-16 carbon atoms, said slurry having a pH ranging from 2.0-6.0 when measured at a total solids concentration of 10 weight percent in the slurry. These controlled pH slurries have improved color and color stability without adverse corrosion characteristics.

This invention relates to aqueous linear alkylbenzene sulfonate compositions. In another aspect, this invention relates to a method for producing these compositions.

For many years, it has been the practice to market aqueous detergent compositions made from the triethanolamide salts of branched chain alkylbenzene sulfonic acids for applications which require mild, nonirritating surface active agents.

These products have customarily been marketed as 60 percent aqueous solutions with a pH of 6.5-7.5. With the industry wide change to biodegradable detergents, triethanolamine salts of linear alkylbenzene sulfonic acids have replaced the branched chain product. Due to solubility or gelling problems, the linear product is sometimes marketed at less than 60 percent concentration, may be marketed as a gel or partial gel, or may contain small amounts of degelling agent such as sodium sulfate or hexylene glycol so that a 60 percent solution can be obtained. The pH of the linear products has been the same as the branched products, i.e. about 65-75.

'It has now been discovered that aqueous slurries having a pH of less than 6.0 have lighter color and greater color stability when compared to similar slurries having a higher pH. These low pH detergents can be further compounded for a wide range of detergent applications such as dishwashing, shampooing or bubble bath. As used throughout this specification and claims, slurry includes solutions, gels and mixtures of solutions and gels. Although it might be expected that corrosion would be a problem with these low pH solutions, it has been found that there is no significant corrosion of 304 stainless steel which is commonly used for storage tank construction.

Therefore, it is an object of this invention to provide aqueous detergent compositions of the triethanolamine salt of linear alkylbenzene sulfonic acids which have lighter color and greater color stability.

It is a further object of this invention to provide aqueous detergent compositions of triethanolamine salts of linear alkylbenzene sulfonic acids which have both low pH and low corrosion characteristics.

It is a further object of this invention to provide a method for preparing aqueous slurries of these detergents.

The detergents which can be utilized in the practice of this invention are the triethanolamine salts of alkylbenzene sulfonic acids having linear alkyl side chains containing from 8-16 carbon atoms and preferably from 3,463,735 Patented Aug. 26, 1969 l0-13 carbon atoms. The method of preparing the alkylbenzene sulfonic acid is not critical to the practice of this invention and can be conducted under any conditions suitable for alkylation and sulfonation of benzene. For example, the alkylated benzene with a monohalogenated normal paraffin, normal alcohol or a normal monoolefin containing 8-16 carbon atoms in the presence of a suitable alkylation catalyst such as aluminum chloride. The resultant straight chain alkylated benzene can then be sulfonated with sulfonating agents such as oleum, sulfuric acid or sulfur trioxide to form alkylbenzene sulfonic acids.

Sulfonic acids made by SO sulfonation may be directly reacted with triethanolamine in the presence of suflicient water to give the desired final concentration of slurry. After sulfonating with either oleum or sulfuric acid, the spent acid may be settled and the sulfonic acid layer directly reacted with triethanolamine in the presence of the desired amount of water. Alternatively, sulfonic acids from oleum or sulfuric acid sulfonation may be diluted with a hydrocarbon solvent to assist in the separation of spent acid, and then the sulfonic acids extracted from the hydrocarbon solvent with approximately 50/50 methanol/water. The sulfonic acids arethen reacted with triethanolamine, and methanol and water removed by evaporation to make the desired concentrated slurry.

The compositions of this invention are prepared by mixing linear alkylbenzene sulfonic acid with a suflicient amount of triethanolamine in the presence of water to yield an aqueous slurry having a pH ranging from 2.0- 6.0 as measured at a total solids concentration of 10 percent by weight. Preferably, this pH ranges from 4.0- 6.0 and most preferably from 5.0-5.5.

These detergent slurries can be made in any concentration which is convenient for end product use. When, however, the solids concentration exceeds about 45 percent by weight, the slurry becomes very viscous and gels tend to form. This phenomenon can be alleviated by incorporating functional amounts of a degelling and viscosity control agent such as sodium sulfate or hexylene glycol. Preferably, the total solids concentration ranges from 40-70 weight percent and most preferably from 55-65 weight percent.

It is also within the scope of this invention to add minor amounts of other ingredients to the detergent compositions to stabilize the basic properties such as anti-oxidants or heat stabilizers. These ingredients may be added in functional amounts without departing from the scope of this invention.

The following examples are given in order that those skilled in the art may more fully understand how to practice this invention and they should not be construed as limitations upon the invention.

Example 1 A slurry contained 25 percent by volume of alkylbenzene sulfonic acids wherein the alkyl radicals were linear and contained from 10-13 carbon atoms with an average carbon atom content of 11.3. The remaining percent of the slurry Was composed of equal amounts by volume of methanol and water. This slurry was divided and the portions (Slurry Nos. 1-5 were contacted with triethanolamine until the pHs were 7.0, 6.5, 6.0, 5.5 and 5.0 respectively. Sodium sulfate was added to each portion in a concentration of 5 parts per parts of solids. After mixing, substantially all of the methanol and a sufficient amount of water was evaporated to produce concentrated slurries. A portion of each concentrated slurry was then diluted with water until the total solids concentration was 10 percent by weight. The pH of this diluted portion was determined. Initial color evaluations on the concentrated slurries were conducted with a Klett-Summerson colorimeter. A portion of each concentrated slurry was stored in light at 75 F. for 12 weeks and the color was then measured according to ASTM Test Dl50064. Another portion of each concentrated slurry was stored in darkness for 6 days at 170 F. and the color was measured by the same ASTM test. These results are reported in Table 1.

TABLE 1 Slurry number 1 2 3 4 5 pH at percent total solids concentration 7. 1 6. 8 6. 2 5. 7 5. 3 Percent total solids after concentrating slurry 63. 3 62. 5 63. 0 62. 7 62. 4 The Klett-Summerson 1 color 395 360 365 290 225 ASTM color after 6 days in darkness at 170 F. 2 L3. 0 L2. 5 L2. 5 L1. 5 L1. 5 ASTM color after 12 weeks in light at 75 F1. L3. 0 2 1. 5 Li. 5 0.5

l The Klett-Summerson color test was conducted as follows: A No. 42 blue filter was placed in a Klett-Summerson photoelectric calorimeter having a 100 watt light source. The instrument was adjustd to 0 using a 40 milliliter glass cell filled with distilled water. The concentrated slurry was then placed in a similar cell and the instrument was readjusted to 0 The Klett-Summerson color value was then read directly from the scale This value is a measure of the light absorptivity properties of the slurry with the higher numbers signifying greater light absorption.

ASTM 13-1500-64: The values are determined in increments of 0.5. L means that the actual value is less than the number given but greater than the next lowest increment.

From the above data, it is demonstrated that the slurries having a pH of less than 6.0 have lighter color and greater color stability. Similar slurries were prepared at pHs of 7.0, 6.0, 5.0, 4.0 and 3.0. The slurries having a pH in the range of 3.0 to 6.0 had Klett-Summerson colors consistently lighter than the slurry having a pH of 7.0.

Example 2 Coupons having approximately 5 square inches in total area were made from T-304 stainless steel. Three sulfonic acid slurries prepared in accordance with Example 1 were contacted with sufiicient tn'ethanolamine to raise the pH to 2.0, 4.0 and 7.0. 5 weight percent sodium sulfate based on solids Was added and the slurries were concentrated until the total solids content was 63 percent by weight. The stainless steel coupons were then immersed in these slurn'es for 19 days at 150 F. The coupons were then visually inspected and weighed. No pitting or weight loss was found in any of the coupons.

It can be seen from Example 2 that even concentrated slurries of the triethanolamine salts of linear alkylbenzene sulfonic acids are not corrosive to 304 stainless steel at low pHs and elevated temperatures.

We claim:

1. An aqueous alkylbenzene sulfonate detergent slurry comprising the triethanolamine salt of an alkylbenzene sulfonic acid having a linear alkyl radical ranging from 8-16 carbon atoms, said slurry having a pH ranging from 2.0-6.0 when measured at a total solids concentration of 10 weight percent in the slurry.

2. A composition according to claim 1 wherein the linear alkyl radical contains from 10-l3 carbon atoms.

3. A composition according to claim 1 wherein the pH ranges from 4.0-6.0.

4. A composition according to claim 1 wherein the pH ranges from 5.0-55.

5. A method of producing an aqueous alkylbenzene sulfonate detergent slurry comprising mixing an alkylbenzene sulfonic acid having a linear alkyl radical containing from 8-16 carbon atoms with triethanolamine in an amount sufficient to raise the pH of the slurry to a value ranging from 2.0-6.0 measured at a total solids concentration of 10 weight percent in the slurry.

6. A method according to claim 5 wherein the linear alkyl radical contains 10-13 carbon atoms.

7. A method according to claim 5 wherein the pH is raised to a value ranging from 4.0 to 6.0.

8. A method according to claim 5 wherein the pH is raised to a value ranging from 5.0 to 5.5.

References Cited UNITED STATES PATENTS 2/ 1967' De Witt et a1 252-l52 3/l967 Michaels et al. 252-152 U.S. Cl. X.R. 25216l 

